JPH0822772B2 - Method for producing translucent ferrite polycrystalline body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a translucent ferrite polycrystal, and more particularly to a method for producing a garnet-type ferrite polycrystal used as a magneto-optical element such as an optical isolator. is there.

(Prior Art) Conventionally, as a garnet-type ferrite crystal used as a magneto-optical element, a single crystal body has been used because a polycrystalline body has pores and the like remaining at grain boundaries and is difficult to transmit light. Although the garnet-type ferrite single crystal has good light transmittance without pores and the like, it is difficult to manufacture because it easily contains impurities, and there is a problem that the cost becomes high.

Therefore, in recent years, a technique for improving the light transmittance in a garnet-type ferrite polycrystal used for a magnetic field sensor is disclosed in Japanese Patent Laid-Open No. 63-163,815. That is, in this technique, in order to reduce the pores of the polycrystal and reduce the light absorption coefficient to the same extent as that of the single crystal, Ca is added first, and V or the like is further added to neutralize the valence. There was a need.

(Problems to be Solved by the Invention) However, in the technique disclosed in the above-mentioned JP-A-63-163,815, although the light transmittance is good, Ca
Since the addition is performed, there is a problem that the magneto-optical characteristics such as the Faraday rotation angle and the Verdet constant are deteriorated. Also, Ca, V
However, there is a problem in that the mixed element is increased by the addition of such as, and the sintered body becomes inhomogeneous. Furthermore, in this polycrystalline body, a liquid phase is easily generated due to the presence of Ca, and there is a problem that it is difficult to form a single crystal by a conventionally known method.

The object of the present invention is to solve the above-mentioned problems, and it is possible to achieve high density without adding Ca or the like, and as a result, not only the optical transparency but also the magneto-optical characteristics such as Ferday rotation angle and Verdet constant are good. It is intended to provide a method for producing a translucent ferrite polycrystalline body.

(Means for Solving the Problem) The method for producing a translucent ferrite polycrystalline body according to the present invention is 2
Ferrite powders having different types of similar composition,
One of them is higher than the target composition and the other is lower than the target composition By mixing the ferrite powder at a predetermined ratio, the composition of the ferrite powder was controlled to ± 0.05 mol% or less with respect to the target value. It is characterized in that the powder is compacted and fired and then hot isostatically pressed to increase the density.

In addition, the method for producing a translucent ferrite polycrystalline body of the present invention is a method for producing two ferrite powders having different compositions and having different compositions, one of which is higher than a target composition and the other of which is a target composition. By mixing lower ferrite powder at a predetermined ratio, the composition of the ferrite powder is controlled to ± 0.10 mol% or less with respect to the target value, after molding and firing, using an atmosphere gas containing oxygen. It is characterized by performing hot isostatic pressing.

Here, the ferrite garnet is represented by the general formula A ₃ B ₅ O ₁₂ , where A is Y and rare earth elements (La, Ce, Pr, Nd, P
m, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), Bi, Ca, Pb etc., B
As the basic element of Fe, Al, Ga, In, Sn, Zr, Ti, Ge,
Includes V, Sb, Sc, etc. Furthermore, the “target value” means A: B = 3 in A ₃ B ₅ O ₁₂ of the crystal structure (composition) of garnet.
7.50: 62.50. A garnet single phase is obtained only when the sum of the number of moles of the elements contained in A and the sum of the number of moles of the elements contained in B are close to this target value, and the second phase is present in other cases. That is, the solid solution range is very narrow.

(Working) In the above-mentioned structure, the composition of the ferrite powder is controlled to ± 0.05 mol% or less with respect to the target value, and the molded body obtained from this powder is fired after hot isostatic pressing (HIP).
Porosity 0.01% or less, wavelength 1.3 μm by treatment
It was found that it is possible to obtain a ferrite polycrystalline body having a good characteristic that the light absorption coefficient at 50 cm ^-1 or less. Here, it is necessary to set the composition of the ferrite powder as a raw material within the range of ± 0.05 mol% with respect to the target value, as will be apparent from Examples described later, even if it is outside this range, This is because even if HIP processing is performed, a sufficient light transmittance cannot be obtained.

At that time, as a method of controlling the composition, two kinds of garnet-type ferrite powders having different compositions and having different compositions, that is, a powder having a large content of a certain element and a powder having a small content of one element, one of which is higher than the target composition and the other of which is higher If the ferrite powder having a low ratio is mixed at a predetermined ratio, the target value of the present invention is ± 0.05.
% Accuracy can be achieved more easily.

Further, since the polycrystal obtained in the present invention does not substantially contain Ca, it does not adversely affect when a known single crystal is joined to form a polycrystal.

The light absorption coefficient α can be obtained from the following equation.

Where I ₀ : intensity of incident light (excluding reflection) I: intensity of emitted light l: length of polycrystal (cm).

Further, an atmosphere gas containing oxygen, preferably oxygen
When hot isostatic pressing is performed using an atmosphere gas containing 0.1% or more, the decomposition and melting temperature of garnet rises, making it possible to raise the sintering temperature and facilitate sintering, further eliminating residual pores and transmitting light. The composition ratio of the ferrite powder is wider than the target value ± 0.10 mol% or less of ± 0.05 mol% with respect to the target value in a preferable example. It is preferable because it can be in a wide range.

(Example) Hereinafter, the present invention will be described in detail.

First, a method for producing a garnet-type ferrite powder as a raw material will be described. In the present invention, as long as a garnet type ferrite powder having a predetermined composition can be obtained, there is no problem in any manufacturing method, but the two methods by the coprecipitation method described below are particularly preferable.

That is, (1) from a mixed aqueous solution containing at least divalent iron ions and yttrium or rare earth metal ions,
A method of coprecipitating a hydroxide with a base, then synthesizing a coprecipitate while oxidizing iron to trivalent, and then separating, drying and calcining, and (2) at least trivalent iron nitrate and yttrium or rare earth A method is preferred in which a mixed aqueous solution containing a nitrate of a metal is used as a raw material, and the mixed aqueous solution of a metal salt is dropped into an aqueous solution of a base to coprecipitate a hydroxide, followed by separation, drying and calcination.

Next, the powder thus obtained is not more than ± 0.05 mol% with respect to the target value, and is not particularly limited when hot isostatic pressing is performed in an atmosphere gas containing oxygen, but preferably ± 0.10 mol. Control so that it is less than or equal to%. In the present invention, the accuracy is ± 0.05 mol% or less of the target value, in a preferred example in the case of hot isostatic pressing in an atmosphere gas containing oxygen, in order to prepare ± 0.10 mol% or less, the following: The compounding correction method described is used. That is,
For example, description will be made on the case where Y ₃ Fe ₅ O ₁₂ crystals are targeted for a composition of Y 37.5 mol% and Fe 62.5 mol%. In this case, powder A (Y38 mol%, Fe62 mol%) and powder B (Y37 mol%, Fe
63 mol%) and mixing powder A and powder B in different proportions, the deviation of each value from the target values (Y37.5 mol%, Fe62.5 mol%) is ± 0.05. It is controlled to be in the range of mol%. It is desirable that the difference in mol% between powder A and powder B is as small as possible. If the difference is large, it is considered that the powder properties are greatly different and the moldability and sinterability are not good. If you do not take a process such as compounding correction,
It is difficult to control the composition at ± 0.05 mol% or less due to compositional variation factors during the process, especially iron content in the crushing process and volatilization of the bismuth component due to calcination in the bismuth substitution product.

Next, the garnet-type ferrite powder for which the mixing and correction has been completed is molded into a predetermined shape and then fired once. Then, the garnet-type ferrite polycrystal, which is the target of the present invention, can be obtained by HIPing in an inert gas such as argon or nitrogen gas or HIPing in an atmosphere gas containing oxygen.

Thereafter, in order to obtain a single crystal from the obtained garnet-type ferrite polycrystal, a method by solid phase reaction is preferable, one example of which is the single crystal garnet disclosed in JP-A-63-35496 by the present applicant. A body manufacturing method can be preferably used.

 Hereinafter, an actual example will be described.

Example 1 Two kinds of synthetic powders A (B in molar ratio were prepared by a coprecipitation method using bismuth nitrate, iron nitrate and yttrium nitrate as starting materials.
i: Fe: Y = 12.0: 62.5: 25.0) and B (molar ratio Bi: Fe: Y
= 13.0: 62.5: 25.0) to produce, BiY ₂ by these powders be formulated correcting by changing the mixing ratio as described below
Fe ₅ O ₁₂ (Bi 12.5 mol%, Fe 62.5 mol%, Y 25.0 mol%) was the target composition.

That is, the synthetic powders A and B were dried, calcined at 800 ° C., pulverized, and then two kinds of powders were wet-mixed at a ratio shown in Table 1 and then dried. These mixed powders are molded and molded at 950 ° C for 10
Burned for hours. The molded body after firing was cut out into a block of 10 × 10 × 7 mm and subjected to hot isostatic pressing at 960 ° C. for 4 hours. From the test piece after hot isostatic pressing, further 7 × 10
After cutting into a shape of × 1 mm and 7 × 10 × 0.3 mm and polishing both surfaces, the light transmittance at a wavelength of 1.3 μm and the Ferday rotation angle were measured.

As Comparative Example 1, bismuth nitrate, iron nitrate, and yttrium nitrate were used as starting materials in a coprecipitation method to obtain a molar ratio of
A powder of Bi: Fe: Y = 12.5: 62.5: 25.0, which was simply synthesized without correction and subjected to the same treatment as that described above, is disclosed as Comparative Example 2 in JP-A-63-163,815. As described above, Ca and V were added (composition Bi ₁ Ca ₁ Y ₁ Fe _4.5 V _0.5 O ₁₂ ), and neither composition correction nor HIP treatment was carried out. ± 0 to the value.
Prepared was a mixture correction of less than 05%, but not HIP treatment. Similarly, the light transmittance and the Faraday rotation angle were obtained respectively. The results are shown in Table 1.

The light transmittance in Table 1 was determined using an optical power meter using a 1.3 μm LED. The Faraday rotation angle was obtained by applying a saturation magnetic field to the element and rotating the analyzer to extinguish the light. In the table, a part without a numerical value indicates that the light transmittance is low and measurement is impossible.

From the results shown in Table 1, mix corrections were made and HIP
Among the test Nos. 1 to 11 in which the treatment was also performed, the test Nos. 7 to 9 in which the accuracy after the compounding correction is ± 0.05 mol% or less have good light transmittance, while the range of ± 0.05 mol% Outside test No.
It can be seen that in 6 and 10, the light transmittance is extremely deteriorated.

Further, Comparative Examples 1 to 3 in which the compounding correction and / or the HIP treatment of the present invention are not performed may be inferior in light transmittance or Faraday rotation angle as compared with the inventive examples of Test Nos. 7 to 9. Recognize.

In the examples of the present invention, mixed powder A: B = 8: 12 of test No. 8
Other magneto-optical characteristics of the element mixed in 1. were measured, and the saturation magnetization was 2100 G and the Verdet constant was 1.3 deg / cm · Oe.

Example 2 Two kinds of synthetic powders A (F in molar ratio were prepared by a coprecipitation method using iron sulfate, yttrium nitrate, and terbium nitrate as starting materials.
e: Y: Tb = 62.0: 30.4: 7.6) and powder B (Fe: Y: Tb = 63.
0: 29.6: 7.4) to produce a by these powders be corrected formulated by changing the mixing ratio as described below, Y _2.4 Tb
_The target composition was _0.6 Fe ₅ O ₁₂ (Fe 62.5 mol, Y 30.0 mol, Tb 7.5 mol).

That is, the synthetic powders A and B were dried, calcined at 1200 ° C., pulverized, and then two kinds of powders were wet-mixed at a ratio shown in Table 2 and then dried. Mold these mixed powders,
Burned for hours. The molded body after firing was cut into a block of 10 × 10 × 7 mm and subjected to hot isostatic pressing at 1500 ° C. for 4 hours. From the test piece after hot isostatic pressing, further 7 × 10
After cutting into a shape of × 1 mm and 7 × 10 × 0.3 mm and polishing both surfaces, the light transmittance at a wavelength of 1.3 μm and the Faraday rotation angle were measured.

Further, as Comparative Example 4, iron sulfate, yttrium nitrate,
By a coprecipitation method using terbium nitrate as a starting material, a powder having a molar ratio of Fe: Y: Tb = 62.5: 30.0: 7.5 was simply synthesized without any correction, and the same treatment as described above was performed. As disclosed in JP-A-63-163,815 as Comparative Example 5, Ca and V were added (composition Y ₂ Tb _0.5 Ca _0.5 Fe _4.75 V _0.25 O).
₁₂ ) What was subjected to neither compounding correction nor HIP treatment, but was subjected to compounding correction of ± 0.05% or less of the composition with respect to the target value by the compounding correction described as Comparative Example 6, but not HIPing. Was prepared, and the light transmittance and the Faraday rotation angle were similarly determined in the same manner as in Example 1. Second result
Shown in the table.

From the results shown in Table 2, mix adjustments are performed and HIP
Among the test Nos. 1 to 11 in which the treatment was also performed, the light transmittance is good in Test Nos. 3 to 5 in which the accuracy after the compounding correction is ± 0.05 mol% or less, whereas the range of ± 0.05 mol% Outside test No.
It can be seen that the light transmittances of 2 and 6 are extremely deteriorated.

Further, Comparative Examples 4 to 6 in which the compounding correction and / or the HIP treatment of the present invention are not performed are inferior in the light transmittance or the Faraday rotation angle to the invention examples of Test Nos. 3 to 5. Recognize.

In the examples of the present invention, mixed powder A: B = 12: 8 of Test No. 4
Other magneto-optical characteristics of the element mixed in 1. were measured, and the saturation magnetization was 1800 G and the Verdet constant was 0.18 deg / cm · Oe.

Example 3 Garnet powders having the compositions shown in Test Nos. 1 to 10 in Table 1 were synthesized by a coprecipitation method using a nitrate or sulfate aqueous solution as a starting material and a powder mixing method using an oxide powder as a starting material. Then, they were calcined, crushed and molded in the same manner as in Example 1, baked at each temperature shown in Table 3 for 1 hour, and then cut to obtain a sample block. The obtained sample block was HI in an atmosphere gas containing Ar gas and 0.1, 1, 5, 20% oxygen.
P treated.

The absorption coefficient and the Faraday rotation angle of the obtained test piece were measured in the same manner as in Example 1. Since the Faraday rotation angle does not change depending on the gas atmosphere used, its representative value is shown. In addition, test No. 9 and 10 containing Ca
In the above, as a conventional example, a case without HIP treatment was also tested. The results are shown in Table 3.

From the results in Table 3, it was found that the HIP treatment in an oxygen atmosphere was effective for all the samples. Also, C
In Test Nos. 9 and 10 including a, the effectiveness of HIP treatment in an oxygen atmosphere was confirmed.

Example 4 As in Example 1, two types of synthetic powders A and B were used, and after mixing and correction as shown in Table 4, oxygen was adjusted to 0.1, 1, 1.
Test pieces of Test Nos. 1 to 16 were obtained under the same conditions as in Example 1 except that the HIP treatment was performed in an atmosphere gas containing 5,20%. The absorption coefficient and the Faraday rotation angle of the obtained test piece were obtained in the same manner as in Example 1, and the accuracy after blending correction is also shown in Table 4.

From the results in Table 4, HI in the atmosphere gas containing oxygen
Among the test Nos. 1 to 16 in which the P treatment was performed and the compounding correction was performed, the composition range wider than that in Examples 1 and 2, that is, the test No. 5 to which the accuracy after the compounding correction is ± 0.10 mol% or less.
No. 11 has good light transmittance, and this range is a preferable range, and other test Nos. 1 to 4 and Nos. 12 to 16
It can be seen that the effect of oxygen HIP increases as the oxygen concentration increases.

(Effects of the Invention) As is clear from the above description, according to the method for producing a translucent ferrite polycrystalline body of the present invention, the composition of the ferrite powder as a raw material is adjusted to an error within a predetermined range by the compounding correction. Along with the hot isostatic pressing,
Furthermore, by performing hot isostatic pressing in an oxygen atmosphere, it is possible to obtain a garnet-type ferrite polycrystal having good light transmittance and good magneto-optical characteristics such as Faraday rotation angle and Verdet constant.

Claims (2)

[Claims] 1. Mixing two kinds of ferrite powders having different compositions and having different compositions, one of which is higher than a target composition and the other of which is lower than the target composition at a predetermined ratio. The powder whose composition of the ferrite powder is controlled to ± 0.05 mol% or less with respect to the target value by
A method for producing a translucent ferrite polycrystalline body, which comprises densifying by hot isostatic pressing after molding and firing. 2. Ferrite powders of two different compositions having different compositions, one of which is higher than a target composition and the other of which is lower than the target composition is mixed at a predetermined ratio. The powder whose composition of ferrite powder is controlled to ± 0.10 mol% or less with respect to the target value by
A method for producing a translucent ferrite polycrystalline body, which comprises hot isostatic pressing using an atmosphere gas containing oxygen after molding and firing.